Performance: L6 vs. W2?

[Phillip Patton]

I have a question about the differences between strength (W2) and impact toughness (L6) in regards to edge deformation. Here's the problem: most of the L6 blades I've made did not hold up well to chopping hard material. (wood) The edges always deform. I've tried changing the edge geometry, and changing the heat treat, but it always behaves the same for me. On the other hand, I've never had a problem with edge damage with W2, O1, 1084, or 1095.

I'd like to make the L6 work, because the high toughness is very attractive, but so far, no good.

 

[Kevin R. Cashen]

This is a real riddle Phillip, since I have experienced quite the opposite as far as L6 is concerned. It does stand to reason that W2 or O1 will have better edge retention due to wear resistance, and that has been my experience. however L6 should have, and has shown in my testing to have, around twice the impact strength of 1095 and 1084 at equivelent hardness. Is this Crucible L6 (champalloy) you have worked with?

It sounds like you may have a lower as-quenched HRC. Edge geometry can factor big time with how the properties play out. As-quenched you should max out at 63 HRC with L6 while the other steels you mentioned will easily reach 65 HRC, depending on geometry and tempering the final hardness of each would factor in. But then if we are talking about deformation, that would be a factor not in oppostion to impact toughness, while strength to resist deformation would bring us back to overall hardness for the given geometry. I have not encountered gross deformation problems in L6, only less wear resistance, which could be considered ductility on a very small scale.

How has your experience with 5160 compared? I personally don't use L6 by itself for blades shorter than around 8" or ones intended for fine cutting and slicing, only large choppers and swords. 1095, O-1 and W2 have proven themsleves as winners for the fine cutters and slicers.

 

[jdm61]

Interesting. Mr. C.......would this be an issue of tempering the blade at too high of a temperature? I wouldn't think that getting an L6 blade fully hard would be an issue considering that Phillip uses much more "finicky" shallow hardening steels quite a bit. I had an issue like this with a Admiral 1075 blade., but I figured that it was a combination of not fully hardening and tempering the steel whihc is actually closer to 1065 in carbon content the way I would temper 1084.

 

[Phillip Patton]

This is a real riddle Phillip, since I have experienced quite the opposite as far as L6 is concerned. It does stand to reason that W2 or O1 will have better edge retention due to wear resistance, and that has been my experience. however L6 should have, and has shown in my testing to have, around twice the impact strength of 1095 and 1084 at equivelent hardness. Is this Crucible L6 (champalloy) you have worked with?

Yes, it is Crucibles L6.
When you say "impact strength", are we talking resistance to breakage, or resistance to deformation?

It sounds like you may have a lower as-quenched HRC. Edge geometry can factor big time with how the properties play out. As-quenched you should max out at 63 HRC with L6 while the other steels you mentioned will easily reach 65 HRC, depending on geometry and tempering the final hardness of each would factor in. But then if we are talking about deformation, that would be a factor not in oppostion to impact toughness, while strength to resist deformation would bring us back to overall hardness for the given geometry. I have not encountered gross deformation problems in L6, only less wear resistance, which could be considered ductility on a very small scale.

It's been a year or so since I tried with the L6, so I don't remember the exact details, but I think the as quenched hardness was around 64. When I tempered at 400, the hardness would go down to 58-59. Even at 62 Rc, the edge would wrinkle when chopping osage orange.

 

[Phillip Patton]

How has your experience with 5160 compared? I personally don't use L6 by itself for blades shorter than around 8" or ones intended for fine cutting and slicing, only large choppers and swords. 1095, O-1 and W2 have proven themsleves as winners for the fine cutters and slicers.

I don't use 5160 much. Because of my experience with L6, I've come to favor the higher carbon steels for everything I make (except swords).

I used 5160 for the JS test because I wanted something that would bend/flex 90 degrees.

But I do have a couple early knives I made that I use often, and I have noticed the edges wrinkling some.

 

[Kevin R. Cashen]

Yes, it is Crucibles L6.
When you say "impact strength", are we talking resistance to breakage, or resistance to deformation?




It's been a year or so since I tried with the L6, so I don't remember the exact details, but I think the as quenched hardness was around 64. When I tempered at 400, the hardness would go down to 58-59. Even at 62 Rc, the edge would wrinkle when chopping osage orange.

Now that is interesting and a bit of a mystery. I apologize for using the term "impact strength" , it is a bit confusing. I do mean toughness, which would be resitance to breaking, not necesarrily deforming, but that is why L6 should have the edge over other steels since it's alloying will allow it almost twice the impact toughness at equivalent hardness which will also equate to strength in resisting deformation.

Some steels will be tough due to lower carbon content, like 1050, 1060, or 5160 (with a mild alloy boost), but along with this gain in toughness will also come the lower strength from lower hardness, L6 can overcome this without the inherent brittleness.

64 seems high for L6, what was your quenchant? 58-59 at 400F is also a more drastic drop than I have experienced. If somebody else had told me this I would put the clues together to indicate a lack of total solution and a more drastic than usual quench resulting in a mixed microstructure with a lot of strain induced hardness that quickly dissipates on tempering. But coming from you I have to scratch my head a bit.

Joe you are correct that whenever I get questions about somthing like O-1 or L6 not behaving as if it is fully hard, I can almost just skip over questioning the quench and go to issues of austenization, since these steels will almost harden from just spitting on them.

 

[Phillip Patton]

Now that is interesting and a bit of a mystery. I apologize for using the term "impact strength" , it is a bit confusing. I do mean toughness, which would be resitance to breaking, not necesarrily deforming, but that is why L6 should have the edge over other steels since it's alloying will allow it almost twice the impact toughness at equivalent hardness which will also equate to strength in resisting deformation.

Some steels will be tough due to lower carbon content, like 1050, 1060, or 5160 (with a mild alloy boost), but along with this gain in toughness will also come the lower strength from lower hardness, L6 can overcome this without the inherent brittleness.

64 seems high for L6, what was your quenchant? 58-59 at 400F is also a more drastic drop than I have experienced. If somebody else had told me this I would put the clues together to indicate a lack of total solution and a more drastic than usual quench resulting in a mixed microstructure with a lot of strain induced hardness that quickly dissipates on tempering. But coming from you I have to scratch my head a bit.

Joe you are correct that whenever I get questions about somthing like O-1 or L6 not behaving as if it is fully hard, I can almost just skip over questioning the quench and go to issues of austenization, since these steels will almost harden from just spitting on them.

Yep, I'm completely baffled myself. I soaked the blades at varying temps (1500-1550) for varying times (5 minutes to 25 minutes) and got the same results. My quench is Parks AAA. The last blade I did I water quenched, just for the heck of it. No cracks in the blade but the tang had some. It got pretty hard, but I never tried cutting with it, so I don't know how it cut at that point.

 

[mete]

How sure are you that it is in fact L-6 ?? Have you done chemistry or even a spark test with another piece ? You will get complete austenitizing in 25 minutes certainly.

 

[Phillip Patton]

How sure are you that it is in fact L-6 ?? Have you done chemistry or even a spark test with another piece ? You will get complete austenitizing in 25 minutes certainly.

Yes, it's definitely L6. I had the same thought when I was working with it, and had a sample tested. I've also used it in damascus, and it has good contrast like L6.

 

[David Wesner]

Yes, it's definitely L6. I had the same thought when I was working with it, and had a sample tested. I've also used it in damascus, and it has good contrast like L6.

Phillip, if you get a minute, could you please PM or email me in regards to who & where you had your steel sample tested ? I have some steel I need to have checked and have been having difficulty finding a source. Thanks

 

[Don Hanson III]

Phillip, this is odd. I have never heard of L6 acting this way and I've never used any either.

Howard Clark would also be a good one to run this past. His work with L6 swords is huge.
You may want to post this question on Don Fogg's forum.